1. Field of the Invention
The present invention relates to an imaging device, a lens drive control method and a recording medium.
2. Description of the Related Art
Conventionally, user's manipulation of an external lever or the like changes over the image magnification powers and focal distances of a camera-mounted cellular phone and a camera unit for which miniaturization and flattening are demanded. There is a camera unit which has a downsized step motor and an AF (Auto Focus) function of moving an imaging lens by the step motor.
The use of a step motor limits the miniaturization of a camera unit. In place of this type of camera unit, recent camera units have a piezoelectric element (piezo element) which is used to move a lens. Using the piezoelectric element makes it possible to further lighten and miniaturize the camera units. Piezoelectric elements have a deformation characteristic in accordance with an applied voltage. A camera unit with the piezoelectric element having such a characteristic applies an appropriate voltage to the piezoelectric element to deform the element, thus driving an imaging lens. A device which drives a lens by a piezoelectric element is disclosed in, for example, Unexamined Japanese Patent Application KOKAI Publication No. 2004-294759.
The vibration of a vibration type actuator using the piezoelectric element becomes driving force to move the lens. Because the lens is movable in a vibration direction, if an external shock or the like is applied to the lens and a lens drive device after the lens is moved to a right position, the lens is moved to a wrong position. Shooting in this state raises problems such that a zoom magnification differs from one desired by a user and a focus is missed. Such problems may be overcome by providing some mechanism for fixing a lens at the correct position, which would enlarge the lens drive device and complicate control of lock/release of the lens.
Those problems are not limited to a camera-mounted cellular phone, and also arise in an optical system using the vibration type actuator.